Related Articles

He is not thought to have explained the motive for his behaviour, but the two men are said to have developed an intense rivalry as Mr Mould became ever more famous and feted.

In 2007 Mr Weiss was among the bidders for a 16th century portrait of Elizabeth I at a Sotheby’s auction, but lost out to Mr Mould, 51, who paid £2.6 million, more than double the upper estimate for its sale price.

Later the same year Mr Mould, who is regarded as a master of self-promotion, opened a gallery near Mr Weiss’s premises, and asked his friend Dr David Starkey to curate an exhibition of Tudor portraits.

Already known for his knack of discovering lost art treasures, including four Gainsboroughs, he published a book in 2009 called Sleuth: The Amazing Quest for Lost Treasures. It was soon after this that he found himself under attack from an anonymous source.

It began with alterations to his online Wikipedia entry, questioning the importance of “discoveries” and suggesting other dealers had made far more important finds – including the Weiss Gallery.

Then, in October 2009, the same person sent a “press release” to national newspapers, falsely claiming Mr Mould was having an affair with Charlotte Barton, a 42-year-old artist.

When the art press received a tip-off that Mr Mould did not have the funds to pay for the painting, sent by someone using the same pseudonym as the author of the previous slurs, Mr Mould and Dr Bader brought in private investigators, who quickly reported back that Mr Weiss was responsible.

Dr Bader, a chemist from Canada, told the London Evening Standard: “I have not received a direct letter of apology from Mr Weiss though I did receive a copy of (his) letter to Philip Mould. Naturally I am not happy with this entire matter.”

The Society of London Art Dealers confirmed Mr Weiss had resigned his membership and his name no longer appears on its website’s list of approved dealers.